Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

Mars 5 was the sister orbiter to Mars 4. After two midcourse corrections on 3 August 1973 and 2 February 1974, Mars 5 successfully fired its main engine at 15:44:25 UT to enter orbit around the planet. Initial orbital parameters were 1,760 x 32,586 kilometers at 35°19'17'' inclination.

Soon after orbital insertion, ground controllers detected the slow depressurization of the main instrument compartment on the orbiter-probably as a result of an impact with a particle during or after orbital insertion. Calculations showed that at the current rate of loss of air, the spacecraft would be operational for approximately three weeks.

Scientists drew up a special accelerated science program that included imaging of the surface at 100 meters resolution. Five imaging sessions between 17 and 26 February 1974 produced a total of 180 frames of 43 usable photographs. Additionally, Mars 5 took five panoramas of the surface. The last communication with Mars 5, when the final panorama was transmitted back to
Earth, took place on 28 February 1974, after which pressure in the spacecraft decreased to below working levels.

Mars 5 photos, some of which were of comparable quality to those of Mariner 9, clearly showed surface features that indicated erosion caused by free- flowing water. Mars 5 was supposed to act as a data relay for the Mars 6 and Mars 7 landers but was obviously unable to do so.

Key Dates

25 Jul 1973: Launch

12 Feb 1974: Entered Mars Orbit

Status: Partial Success

Fast Facts

This was a sister spacecraft to Mars 4.

It was the third Soviet spacecraft to orbit Mars.

Scientists planned an accelerated science mission after the spacecraft was damaged by an impact in orbit.